Manufacture of fluorochloromethanes



Oct. 30, 1951 l J. D. ALFEE ErAL MANUFACTURE 0F FLUOROCHLOROMETHANES su@ ...l

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INVENTORS. JOHN D. CALFEE LEE B. SMITH ATTORNEY.

Patented Oct. 30, '1951 MANUFACTURE F FLUOROCHLORO- METHANES John D. Calice, Manhasset, N. Y., and lee B. Smith, Woodbridge, N. J., assignors to Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York Application April 21, 1949, Serial No. 88,792

Claims. (Cl. 260-653) This invention relates chiefly to the manufacture of dichlorodiiluoromethane, CClzFz, trichloroiluoromethane, CClsF, and tetrachloroethylene, CCl2=0Clz, by chlorinolysis (disunion of carbon atoms by the action of chlorine) of 1,1- diiluoroethanes.

It has been proposed to produce CClzFz and CClzF by a two-stage process comprising rst subjecting a mixture of the 1,1-diuoroethane, ethylidene fluoride (CHJCHFz), and chlorine to the action of actinic radiation to produce at least monochlorinated 1,1-difluoroethanes such as CHaCClFz. In the second stage, the product mixture of the photochemical treatment and possibly additional amounts of chlorine, are subjected Ato pyrolysis, i. e., temperatures in the range 550-950 C., thereby causing substantially exhaustive chlorination and disunion oi' the carbon atoms. The product of the second stage comprises CClzFa and CClsF as primary sought-for products, 0014 and, in addition. some 02014. As an alternative procedure for producing CClzFa and CClsF, ethylidene iluoride may be directly subjected to chlorinolysis, without any preliminary treatment with actinic radiation, under conditions relatively similar to those employed in the second stage of the previously mentioned procedure. The product mixture comprises CClaF'z, 00131, 0014, and some C2014. Other 1,1-diiluoroethanes, such as chlorinated ditluoroethanes, may be used as starting material with substantially similar results in which case the amount of chlorine added is modiiled to allow for the chlorine already present in the molecule. These operations are characteristically such that chlorine consumption and the amount of chlorine in the loff-gas in some operations may be relatively high, e. g. 10% by volume.

The foregoing processes are decided improvements over prior art methods of producing dichlorodiuoromethane. However, in the proposed procedures, it would be desirable if possible to convert the carbon tetrachloride byproduct to other product or products having greater commercial value, and to reduce the amount of free chlorine which appears in the oilgas from the chlorinoly sis treatment, and thereby simplify puriilcation procedures.

Particular objects of our present invention are to convert carbon tetrachloride produced by chlorinolysis of l.ldiiluoroethanes eillciently into other products of greater value and, further, to provide practical means for reducing the amount of chlorine in the olf-gas without decreasing the yield of desired products or otherwise detrimentally affecting the process.

2 According to our invention the process of subjecting a mixture of a 1,1-dii1uoroethane and chlorine to pyrolysis conditions to obtain a product comprising CClzFz, CClsF and C014 is modied by separating at least part of the 001i from the product mixture and adding it to the dip iluoroethane-chlorine mixture before the latter is subjected to pyrolysis. A normal expectation of the eiect of such. procedure would be that the space velocity of the main process stream would have to be decreased and that the yield of desired products would be materially adversely ailected. Further, it would be expected that any reaction that the recycled C014 might undergo would disturb the thermal balance of the system. Surprisingly, we have found that nc such disadvantages are attendant with recycling C014` to chlorinolysis reactions. Further, as a more particular advantage of our process, we nd, unexpectedly, that C014 is largely converted to a more valuable product, C2014. Thus, even though all of the C014 produced is continuously separated from the product and returned to the chlorinolysis step, there is no excessive build-up of 0014 in the system. The 02014 product obtained has greater commercial value and accordingly we normally separate the entire amount of C014 from the product and add it as recycle material to the chlorinolysis reaction. However, our process is not limited to thus separating and recycling the entire amount of C014 formed. It is within the scope of our invention to separate part only, of the C014 for the recycling procedure. As will be apparent to those skilled in chemical technology, C014 may be readily available in commercial operation from sources other than the chlorinolysis procedures described Y above. Hence, it may be desired to add 0014 from other sources to the chlorinolysis reaction and such operation is intended to be included product, comprising a substantial quantity of 1,1,1-di1luorochloroethane, usually substantial possibly high values of e. g. by volume. 'I'he quantities 'of more highly chlorinated materials,

feature of enabling the reduction in the chlorine produced by subjecting thel,ldiuoroethane chlorine mixture to the action of lactinic radiation is a starting material employed to obtain the marked advantages of our novel process. Our improved procedure, although n t limitedl to continuous chlorinolysis operations, is advantageously applied thereto. Accordingly, we more preferably carry out our process in two steps comprising first continuously subjecting a mixture of CHaCHFa andtchlorine to the action of actinic radiation thereby to obtain the reaction mixture containing residual free chlorine and -intermediate product comprising at least monochlorinated 1,1-diiluoroethane, and second. continuously subjecting this reaction mixture to pyrolysis in the presence of chlorine to produce CClzFa, CClsF and C014. this product and added to the reaction mixture before the latter is subjected to pyrolysis.

The latter preferred embodiment of our invention will be more clearly understood by referring to the attached Figure l, which is a representation thereof in diagrammatic form. Chlorine and ethylidene uoride, lflowing from their respective containers, are mixed and caused to undergo reaction in the annular reaction space of the photochlorination unit I. The gaseous product, consisting of chlorinated 1,1-difluoroethanes, such as 1,1,1-diuorochloroethane and some more highly chlorinated ethanes, and chlorine, may be fortified by further addition of chlorine through pipe 2. The recycle is added from pipe 3 and the mixture passes through chlorinolysis unit l. The eiiiuent product, comprising CClzFz, CClzF, C014, 0201i, HC1, and unreacted chlorine is passed through cold stripper 5, where the higher boiling materials C014, C2014, and some C0131il are condensed. The .C014 is separated by distillation from this liquid product at 8 and is recycled to the chlorinolysis feed through pipe 3.

In case CHaCHFz is subjected to chlorinolysis directly, without first undergoing photochlorination at I, the CHs=CHF2chlorine mixture may be fed directly to chlorinolysis unit 4' through pipes 2 and 6. Product recovery at 5 and 8 and recycle procedure through pipe 3 is similar to that'described above.

As previously indicated it is an object of our j invention to decrease thechlorine in the product gas and thereby simplify purification procedures. However, if amounts of chlorine reactant employed are decreased substantially below certain values, the formation of appreciable amounts of the unsaturated material, CClif-CCIF, results. This material boils at a temperature very close to boiling temperature of 0014. Such by-product formation causes loss of sought-for products and the difficulty of separation of this unsaturate from C014 by fractional distillation. According to our present invention less amounts of initial chlorine may be employed without causing these effects. 0014 recycled to the chlorinolysis reaction decomposes to produce chlorine and the valuable product 0:7014, the reaction probably proceeding las follows:

200li- 0Cl1=CCln+20h ess material to give sought-for products, thus functioning in the same manner as free chlorine C014 is separated from initially introduced into the reaction. Accordi ingly, the' chlorine initially introduced into the reaction may be decreased. This, in turn, causes a decrease in the concentration of the residual chlorine in the gaseous mixture of products below feed to be made is a particular advantage of our present process.

A further important aspect of our discovery which is a particular feature of a preferred embodiment of our invention is that, .when appreciable amounts of CCl2=C0lF are formed and appear in the product, as is the case, for example,v in processes in which the ratio of added chlorine to the 1,1-difluoroethane starting material is maintained at a low value, the 00h need not be separated from the CCIFCCIF prior to recycling 0014 to the pyrolyzer. 0Cia=CClF may be recycled from distillation unit 8 of Figure 1 through pipe 3 with the 0014. 0Clz=CClF thus recycled is converted to CCnF which is one of the primary sought-for products of the chlorinolysis process for producing CClzFz. Since the principal disadvantageous eiiect of reducing chlorine concentration in the feed mixture is loss of sought-for products as the unsaturate, CClz=CClF. and difficulty of separation of the C014 from this unsaturate, a further'obJect and advantage of the invention now becomes apparent. In the light of our discovery that both 0014. y

olysis of a 1,1 diuoroethane and add such mixture to process material to be subjected to chlorinolysis.

The material to be recycled may be separated from the chlorinolysis product in any suitable way, e. g. by condensation and by distillation of the condensate as in stripper 5 and still 8 of the drawing. The upper limit of the boiling range of the recycle fraction'should be not substantially above about "v C., which temperature limit includes substantially all C014 present (B. P. plus 77 0.). A suitable lower limit of the boiling range is 63 C., since such a fraction would normally include substantially all of the unsaturate CCl2=CClF present (B. P. plus 71 0.). However, in practice, it may be found convenient to return as recycle to chlorinolysis certain amounts of CChF (B. P. plus 23.8 0.), which material passes through the chlorinolysis reactor substantially unaffected. In this case the lower limit of the boiling range of the recycle material may be about 15-20 C.

We have found further, as part of our discovery, that it is not necessary to subject the C014, CCl2=CClF mixture to chlorinolysis conditions in the presence of other material in order to effect conversion of this unsaturate to CClaF. This mixture may, if desired, be treated separatelyin a reactor similar to chlorinolysis unit 4. It appears that the 0014. under these conditions decomposes to produce free chlorine as described above, which chlorine in turn attacks the unsaturate to effect chlorinolysis thereof and to produce the sought-for CChF. Suicient 0014 should be present in the mixture so separately pyrolyzed to produce chlorine in amount sumcient to effect the desired chlorinolysis of the CCh=CClF. If insufdcient C014 is present in the mixture separated from the chlorinolysis product, additional free chlorine may be added to the mixture prior to said chlorinolysis. Further, if it is desired to treat C012=C01F alone, this material may be pyrolyzed in the presence of suicient chlorine to produce CClaF, the reaction conditions being those previously described for the chlorinolysis of 1,1-difluoroethanes.

We believe that the reaction of CClz=CC1F with chlorine to produce CClsF takes place according to the following equation:

i. e., for each mol of CCla=CC1F decomposed (subjected to disunion of the -0 bond), l mol of CClsF is theoretically formed, and assuming complete dimerization of C014, there is also theoretically formed 1/2 mol of CCl2=CCl2. However, our invention is not intended to be limited by any theory of reaction.

Since CClzFz is the preferred main product of the reaction, at least suiilcient chlorine is used to form this product in substantial amounts. In the CCM-recycling procedure, amounts of chlorine to be employed in any particular chlorinolysis operation will depend to some extent upon the operating conditions maintained and upon the particular 1,1-diilu-oroethane starting material fed to the chlorinolysis unit. In general, the amount of chlorine may be less than processes in which no C014 is recycled. For example, when CHaCClFa, is used as chlorinolysis feed material, chlorine to CHaCClFz ratios in the range 2.8:1 to 4.0:1, may be maintained. 1n the event that the starting material is a product of chlorination of 0H3-CHF2 higher than CH3-001m, correspondingly lower amounts of chlorine may be employed in the recycling process of our invention. Ordinarily, when the material fed to the chlorinolysis unit is the product of the photochemical treatment of CH3-0HF2 described above, the range of ratios of chlorine to CH3-CHF2 employed in the overall photochemical and chlorinolysis operation according to the present invention may be 3.8:1 to 5.0:1. When CHzCHFa is employed as starting material for the one step process referred to above, similar low ratios of chlorine to CHa-CHFz may be utilized.

The temperatures which are maintained according to our improved chlorinolysis procedure are substantially the same as those employed for the reaction when no C014 is recycled to the mixture undergoing chlorinolysis. This is-andmportant advantage in our -process because the recycled material can be added to the main process stream without necessitating or causing substantial changes in operating temperature. Broadly considered temperatures in the range 550-950 C. may be employed, but a more preferred range is 650-850 C.

It should be emphasized that, for a given operation, an outstanding and unexpected advantage of our process lies in the fact that recycled material (from pipe 3) may be added to the main process stream without decreasing the rate of throughput of said main process stream (pipe 6). In the recycle procedure, the yield of sought-for CClzFz remains substantially unchanged as compared with yields when no material is recycled. Accordingly, the space velocity which may be employed according to the present invention is the sum of the space velocity of the main process stream when there is no recycle plus the space velocity of the recycled material.

The process may be carried out in a tubular reactor (4) of suitable length, equipped at one end with pipe connections facilitating introduction into the reactor of the desired proportions of raw materials, and at the outlet end with a gas oil-take pipe for conducting the exit gas to the product recovery system. The reactor is provided withy an external heating jacket together with means for maintaining controlled temperatures within the reactor. The reaction preferably should be carried out in the absence of catalysts such as active carbon and compounds of silicon. Hence. the reactor is preferably made of a neutral or non-catalytic material such as graphite.

The exit gas from the step of chlorinolysis of the 1,1-diuoroethane and recycled C014 comprises CClzFz (B. P. minus 30 C.), CClsF (B. P.

plus 23.8 0.), C014 (B. P. plus 77 C.), C2014 (B. P. plus 122 C.) plus HC1 and some unreacted chlorine and may in addition, as previously indicated herein, also comprise C012=CC1F (B. P. plus 71 0.). Such a gas may be treated in any suitable Way to recover the desired products. For example, the gas stream may be passed through stripping apparatus 5 maintained at a temperature sufficiently low (e. g. minus 15 C.) to strip out high boiling materials, e. g. C014, 02014, possibly some CClaF and any 0012=CC1FI present, and then may be water-washed at ilA to remove most of the hydrochloric acid, washed with a mild NaOH solution at I0 to remove chlorine and the last traces of H01, and finally dried at II as by use of calcium chloride or silica gel. The exit gas of the drying step comprises principally 0012F2. If desired, such gas stream may be further cooled at I2 to condense CClzFz and CClaF, and the resulting liquor may be fractionated at I3 to recover CClzFz and CClsF as products. The condensate obtained from stripper 5 plus the bottoms from still I3, may be distilled at 8 to separate and recover the CClsF, C2014 and C014. In the absence of C01z=001F, the 0014 cut may be recovered in substantially pure form, or in the presence of 0Cl2=0ClF a distillate mixture of C014 and CC1z=C0lF may be recovered. The CC14 or the C014, CClz=CClF mixture so distilled from the reaction product may be recycled through pipe 3 to subsequent chlorinolysis procedure. As heretofore indicated, if desired, the recycle cut may also include any CClsF condensed in stripper 5.

For processes in which 0H3=CC1F2 is employed as starting material for the chlorinolysis procedure of our invention, such 0H3-0C1Fz may be prepared by methods other than actinic radiation as heretofore described. For example, methyl chloroform may be uorinated using antimony triuoride as the iluorinating agent to accomplish replacement of two of the chlorine atoms in the methyl chloroform by fiuorine; Similarly, methyl chloroform may be fluorinated using anhydrous hydrofluoric acid as iluorinating agent.

Following are examples illustrating the practice and advantages of our invention process and various phases thereof, the parts and percentages expressed being by weight:

Example 1 164 parts of ethylidene fluoride and chlorine in gaseous form were fed from their respective containers in mol ratio of 4.5 mois C12 per mol CHaCHFz, intimately mixed and introduced into the stage 1 reactor which consisted of an annular space formed by the wall of a tubular uorescent lamp and a cylindrical glass jacket. The

gas mixture was passed through the reactor at about 170 space velocity-hour units while being subjected to light from the fluorescent lamp. 60 v parts of recycle material, which material consisted of 35 weight per cent of C014 and 65 weight per cent of Cl2=00lF, were mixed with the of!- gas from the reactor of stage 1 and the'mixture was passed to the stage 2 reactor which consisted of a graphite tube of such length and diameter that the gases were passed through the reactor at space velocity of 500 S. V. H. The graphite tube was provided with a jacket whereby heat was applied and temperature maintained at about 800 C. The off-gas containing some residual free 0h was passed upward through a packed externally cooled nickel pipe maintained at about minus 15 C. to strip out the high boiling materials C0l4, C2014, 0012=C01F, and some CClaF.

Gas from the stripper, containing 4.76% C12 was scrubbed with water to remove H01, with alkali solution to remove excess chlorine and were dried and cooled sufdciently to liquefy CClzFz and any previously uncondensed CClaF and condensate was collected in a cold trap. CClzFz and CClaF were separated by distillation and recovered. The stripper condensate was distilled and CClaF, C2014, individually, and a mixture of C014 and C0lz=CC1F were recovered. A small residue of higher boiling materials was also recovered. Products recovered: 226 parts CClzFg, 116 parts CClsF, 143 parts 0Cl2=00l2, 31 parts C014 and 22 parts C012=C01F. The CClzFz yield was substantially unchanged, while the CClsF and C2014 yields were substantially increased (illustrating the conversion of the by-products of C0lz=C0lF and 0014 to sought-for CC13F and C2014, respectively) as compared with procedures in which no material was recycled.

Example 2 A liquid product from chlorinolysis of 0H3CClF2 was distilled, and a fraction boiling in the range 65-83 C. was recovered. This fraction was found byl analysis to contain approximately by weight C014, 65% C012=CC1F, the balance consisting of other halogenated hydrocarbons. 170 parts of said fraction (52 parts of C014 and 111 parts of 0Cl2=C0lF) was mixed with about 35 parts of free chlorine and the gaseous mixture fed continuously to a graphite tube reactor at the rate of 125 space velocity hour units. The temperature of the reactor was maintained at about 775 C. The product off-gas was removed at the exit of the reactor, residual free chlorine and HCl was removed therefrom and the product mixture containing CClsF, C014, C2014,

CClz=CClF and other fluorinated products was collected and distilled. Products recovered: 53 parts CClaF, 8 parts 0014, 27 parts CCl2=CClF, 65 parts C2014, 5 parts CClzFz and 9 parts CFChCCla. Of the total C012=C01F which disappeared, 71% was accounted for by formation of CClsF (based on the theoretical formation of 1 mol CClaF per mole CCla=0ClF consumed). On the basis of formation of 1/2 mol of 0Clz=CClz for each mol of 0014 -consumed and each mole of C0lz=CClF decomposed (i. e., C-C bond split), the above data showed that substantially all of C2014 which appeared in the product was accounted for by the disappearance of C014 and CC1z=C0lF.

Example 3 50 parts per hour of ethylidene uoride, and chlorine in amount to afford 4.4 mols of Clz per step 2 as indicated above.

fraction remaining in the still, consisting pre- 8 form from their respective containers. intimately mixed and introduced into a reactor (stage l) which consisted of achamber illuminated by fluorescent lamps The gas mixture was passed through the reactor at about 840 space velocityhour units while being subjected to light from said lamps. To the olf-gas from stage 1, containing CHaCClFz and other more highly chlorinated fluoroethanes, there was added continuously 42.1 parts per 'hour of recycle material separated by distillation from the product of stage 2. The recycle material consisted of 38.7% 0014, 37.8% C01z=CClF, 22.5% CClsF and the balance CaCltV and other high boiling material. The mixture of feed and recycle was passed to the stage 2 reactor which consisted of a graphite tube of such length and diameter that the gases were passed through the reactor at space velocity of 313 S. V. H. The graphite tube was provided with a heating jacket, and temperature of the chlorlnf olysis reaction was maintained at about 793I C. The off-gas containing some residual free Clz was passed upward through a packed externally cooled pipe, maintained at about minus 25 C. to strip out the high boiling materials, 0014, C2014, C0ls'=CClF and some CClaF. Gases from the stripper containing 4.3 weight per cent Ch were scrubbed with waterto remove H01. with alkali solution to remove excess chlorine and were dried and cooled sulciently to liquefy CClaFz and any previously uncondensed CClsF. CClzFz and C0131'I were separated by distillation and recovered. A small amount of C014 was also recovered. The stripper condensate was distilled and a fraction containing C014, CCl2=CClF and CChF, was separated and returned as recycle with the feed to 'I'he higher boiling dominantly of 02014 and a small amount of other high boilers and C014, was recovered. Products recovered (per hour): 69.8 parts 0012Fz, 40.4 parts 001311', 48.8 parts 02Cl4. and 2.3 parts C014. The CClzFz yield was substantially unchanged while the yields of 02014 and CClsF were increased substantially as compared with chlorinolysis procedure in which the reactants and reaction conditions were substantially similar but no material was recycled to the stage 2 reactor. Further, these improvements were obtained notwithstanding the use of an appreciably reduced chlorine input. The foregoing results illustrate the conversion of recycled C014 and C0lz=CClF to more valuable material as hereinbefore described, and also the feasibility of reducing chlorine input. V

Example 4 273 parts of ethylidene fluoride, and chlorine in gaseous form were fed from their respective containers in mol ratio of 4.5 mols 0h per mol CHzCHFz, intimately mixed and introduced into a reactor (stage 1) which consisted of the annular space formed by the wall of a tubular uorescent lamp anda cylindrical glass jacket. The gas mixture was passed through the reactor at about 170 space velocity-hour units while being subjected to light from said lamp. parts of C014 were mixed with the oil-gases from the reactor of stage 1, containing CHs-CCIFz, and the mixture was passed to the stage 2 reactor which consisted of a. graphite tube of such length and diameter that the gases were passed through the reactor at space velocity of 500 S. V. H. The graphite tube was provided with a jacket whereby heat was applied and temperature maintained at mol of CHaCHFn were fed continuously in gaseous 7| about 800 C. The olf-gas containing some residual free Cla' was passed upward through a packed externally cooled nickel pipe. maintained at about minus 15 C. to strip out the high boiling materials CC14, C2C14, CC12=CC1F and some CClaF.

Gases from the stripper containing 6.1 weight per cent C12 were scrubbed with water to remove HCl, with alkali solution to remove excess chlorine and were dried and cooled sufliciently to liquefy CC12F2 and any previously uncondensed CClsF. CClzFz and CClaF were separated by distillation and recovered. The stripper condensate was distilled, and CClaF, C2Cl4, individually, and a mixture of CC14 and CC12=CC1F were recovered. A small residue of higher boiling materials remained in the still. 202 parts C2014, 42 parts CC14, and 12 parts CCl2=CClF were recovered. Even though CC14 was formed during the chlorinolysis reaction. as above described, it will be noted that the amount of CC14 recovered was substantially smaller than that fed to the reactor. This illustrates the facility of conversion of CC14 to other materials as hereinbefore described.

Example 165 parts of ethylidene fluoride, and chlorine in gaseous form were fed from their respective containers in mol ratio of 4.5 mols Cla per mol CHaCHFz, intimately mixed and introduced into the stage 1 reactor described in Example 4. The gas mixture was passed through the reactor at about 170 space velocity-hour units while being subjected to light from the uorescent lamp. 60 parts of recycle material, which material consisted of 80 weight per cent of CC14 and 20 weight per cent of CClz=CClF, were mixed with the oil-gas from the reactor of stage 1 and the mixture was passed through the stage 2 reactor of Example 4 at space velocity of 500 S. V. H. The temperature in the tube was maintained at about 800 C. The off-gas, containing some residual free C12, was passed through a stripper, as described in Example 4, and the gas from the stripper was scrubbed, dried, cooled sufficiently to liquefy CClaFz and any previously uncondensed CClaF and condensate was collected in a cold trap. The stripper and cold trap condensates were fractionally distilled as described in Example 4 to recover CClzFa, CClaF, and C2014 individually, and a mixture of CC14 and A small residue of higher boiling materials was recovered. Products recovered: 230 parts CClzFn, 102 parts CClaF, 140 parts CClz=CCl2, 36.1 parts CC14. and 15.4 parts CClzCClF. The CClzFz yield was substantially unchanged, while the CClaF yield was substantially increased (illustrating the conversion of the by-product CC12=CC1F to CChF) as compared with procedures in which no material was recycled. Notwithstanding formation of CC14 in the reactor, it will be noted that the amount of CC14 present in the product was substantially smaller than that returned with the recycle, thus illustrating the conversion oi CC14 to other materials.

We claim:

1. In the process of pyrolyzing a mixture of a 1,1-diuoroethane and chlorine to form a reaction product comprising CCl2F2, CClsF and CC14l the step which comprises adding CC14 to said mixture before subjecting the same to said pyrolysis.

2. In the process of pyrolyzing a mixture of a 1,1-diiiuoroethane and chlorine to form a reaction product comprising CClzFz, CClaF, and CC14, the improvement which comprises separating at least part of said CC14 from said product, and

adding said separated CCll to said mixture before subjecting the sameto said pyrolysis.

3. In the process of pyrolyzing a 1,1-diuoroethane in the presenceof chlorineto -form a :i'e-

. action product comprising CClzFz, CClsF, CC14 to that boiling substantially in the range of 6385 C. at substantially atmospheric pressure, and adding said mixture to said 1,1-diuoroethane before subjecting the same to said pyrolysis.

5. The process which comprises pyrolyzing a mixture of a 1,1-diuoroethane and chlorine in amount at least suilicient to form CClzFz at temperature in the range of 550950 C. to form a reaction product comprising CClzFn, CClsF, CC14 and CC12=CC1F, separating from said product at least part of said CC14, and adding said separated CC14 to a further quantity oi' said mixture before subjecting the same to said pyrolysis.

6. The process which comprises pyrolyzing a mixture of a 1,1-diiuoroethane and chlorine in amount at least sufcient to form CClzFz at temperature in the range of S50-950 C. to from a reaction product comprising CClzFz, C ClsF, CC14 and CC12=CC1F, separating from said product a mixture of at least part of said CC14 and said CC12=CC1F, and adding such mixture to a further quantity of said lrst mentioned mixture be- -fore subjecting the same to said pyrolysis.

'7. The process which comprises pyrolyzing a mixture of a 1.1-diiiuoroethane and chlorine in amount at least suilcient to form CClzFz at temperature in the range of 55,0-950 C. to form a reaction product comprising CClzFz, CClaF, CC14 and CCl2=CClF, separating from said product a mixture equivalent to that boiling substantially in the range of 63-85 C. at substantially atmospheric pressure, and adding such mixture to a further quantity of said iirst mentioned mixture before subjecting the same to said pyrolysis.

8. In the process of pyrolyzng a mixture of an at least monochlorinated 1,1,difiuoroethane and chlorine to form a reaction product comprising CClzFz, CClaF and CC14, the improvement which comprises separating at least part of said CC14 from said reaction product, and adding said separated CCl4 to said mixture before subjecting the same to said pyrolysis.

9. The process which comprises pyrolyzing a mixture of an at least monochlorinated 1,1-diuoroethane and chlorine in amount at least sufficient to form CClzFz at temperature in the range of 55C-950 C. to form a reaction product comprising CClzFz, CClaF, CC14 and CCl2=CClF, separating from said product a mixture equivalent to that boiling substantially in the range of 63-85 C. at substantially atmospheric pressure, and adding such mixture to a. further quantity of said first mentioned mixture before subjecting the same to said pyrolysis.

10. The process which comprises actinically reacting CHsCHFa and chlorine, in amount at least suicient to form CClzFz, to form a mixture comprising at least monochlorinated CHzCHFz and residual free Clz, pyrolyzing said mixture at temamavis perature in the range of 550-590 C. to form a reaction product comprising CClzFz, CClsF and CC14, separating at least part of said CCl4 from said product, and adding said separated CC14 to a further quantity of said mixture before subjecting the same to said pyrolysis.

11. The process which comprises subjecting to actinic radiation a mixture of CHaCI-IFz and sufcient chlorine to ultimately form dichlorodiuoromethane under conditions to form an intermediate reaction mixture containing residual free chlorine and at least monochlorinated ethylidene fluoride, heating said intermediate mixture at temperature in the range of 550-950 C. in the presence of said residual chlorine to thereby form a reaction product comprising CClzFz, CClaF, CC14 and CC12=CC1F, separating from said reaction product a mixture of at least part of said CC14 and said CC12=CC1F, and adding such mixture to said intermediate mixture before subjecting the same to said heating.

12. The processwhich comprises subjecting to actinic radiation a mixture of CHaCHFz and sufficient chlorine to ultimately form dichlorodiiluoromethane under conditions to form an intermediate reaction mixture containing residual free chlorine and at least monochlorinated ethylidene fluoride, heating said intermediate mixture at temperature in the range of G50-850 C. in the presence of said residual chlorine to thereby form a reaction product comprising CClzFz, CClzF, CC14 and CC12=CC1F, the total amount of chlorine utilized in the radiation and heat steps being in the range of about 3.8 to 5.0 mois per mol of CHaCHFz, separating from said reaction 12 product a mixture equivalent to that boiling substantially in the range of 6385 C. at substanstantially atmospheric pressure, and adding such mixture to said intermediate mixture before subjecting the same to said heating.

13. The process which comprises subjecting CC12=CC1F to a temperature in the'range 550 to 950 C. in the presence of sumcient Ch to form con?.

14. The process which comprises subjecting- CClr=CC1F to a temperature in the range 650 to 850 C. in the presence of suiiicient Clz to form CClaF for a time suillcient to i'orm a substantial quantity of CCL-4F.

15. The process which comprises subjecting a mixture of CCIFCCIF, C014 and C1: to a temperature in the range 650 to 850 C., the aggregate amount of said CC14 and Cla being sumcient to cause the production of a substantial amount of CClsF, for a time sumcient to form a substantial quantity of CClsF.

LEE B. SBMTH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date JOHN n. oma. f Y 

1. IN THE PROCESS OF PYROLYZING A MIXTURE OF A 1,1-DIFLUOROETHANE AND CHLORINE TO FORM A REACTION PRODUCT COMPRISING CC12F2, CC13F AND CC14, 